It has become increasingly common in recent years to place monitoring wells in areas where pollution is suspected of affecting the water supply. Such wells typically extend into the underground aquifer thereby allowing the water to be sampled and tested for contamination.
Since a well of this type is sampled periodically, it is often necessary to leave the well in an undisturbed state when no sampling is being conducted. During such periods, the instrumentation and sampling equipment are removed from the well top leaving it vulnerable to tampering or trespass. Preventing access to the well is particularly critical with monitoring wells since the purpose of such wells is to test and sample the underground aquifer in an undisturbed condition. It is therefore desirable to secure the top of the well and prevent unauthorized access to the well.
Numerous prior art well caps exist in an attempt to secure access to the top of the well pipe. For example, U.S. Pat. No. 4,881,597 to Hensley and U.S. Pat. No. 5,184,608 to Hale, III disclose locking caps which are hinged and include provisions for securing a padlock or other device to the cap. Although these devices succeed in securing the top of the well pipe they are not entirely satisfactory. These devices are attached to the well pipe using grout, glue or other cement which could contaminate the well water and compromise the integrity of the monitoring process. Further, these devices include hinges which are exposed and therefore subject to weathering and eventual failure.
Other types of devices include plugs which incorporate cams that expand a liner against the inner wall of the pipe to secure the plug within the pipe. For example, U.S. Pat. No. 3,618,811 to Martine and U.S. Pat. No. 4,303,101 to Tholen provide wedge devices which are inserted into the end of the conduit and are tightened to cap or plug-off the end of the pipe. These devices are often found in sewer pipes or other conduits and have been found to be unsatisfactory when used in the capping of monitoring wells. The plugs are constructed from varied elastomeric materials which can leach contaminants into the well. Further, the devices do not provide a tamper-proof means for securing or locking the end of the pipe. There are no provisions for attaching a padlock and plug-type devices may be pried off using a screwdriver, chisel or other means. Lastly, these devices do not transmit sufficient locking force to the interior walls of the pipe and tend to loosen up over time due to their flexibility.
A need has therefore existed in the art for a locking cap that secures the open end of a well pipe, prevents contamination of the well, is of simple construction, provides a secure means of attachment and may receive a padlock or other supplementary locking device.